Synergistic osmoregulatory dysfunction during salmon lice (Lepeophtheirus salmonis) and infectious hematopoietic necrosis virus co‐infection in sockeye salmon (Oncorhynchus nerka) smolts

Abstract

While co‐infections are common in both wild and cultured fish, knowledge of the interactive effects of multiple pathogens on host physiology, gene expression and immune response is limited. To evaluate the impact of co‐infection on host survival, physiology and gene expression, sockeye salmon Oncorhynchus nerka smolts were infected with the salmon louse Lepeophtheirus salmonis (V−/SL+), infectious hematopoietic necrosis virus (IHNV; V+/SL−), both (V+/SL+), or neither (V−/SL−). Survival in the V+/SL+ group was significantly lower than the V−/SL− and V−/SL+ groups (p = 0.024). Co‐infected salmon had elevated osmoregulatory indicators and lowered haematocrit values as compared to the uninfected control. Expression of 12 genes associated with the host immune response was analysed in anterior kidney and skin. The only evidence of L. salmonis‐induced modulation of the host antiviral response was down‐regulation of mhc I although the possibility of modulation cannot be ruled out for mx‐1 and rsad2. Co‐infection did not influence the expression of genes associated with the host response to L. salmonis. Therefore, we conclude that the reduced survival in co‐infected sockeye salmon resulted from the osmoregulatory consequences of the sea lice infections which were amplified due to infection with IHNV.

Antimicrobial Peptides of Salmonid Fish: From Form to Function

“…IHNV also upregulates hepc mRNA in the kidneys of Sockeye salmon ( Oncorhynchus nerka ); although not confirmed, this may be attributed to IL-6 signaling, such as in mammals [ 62 , 63 ]. IHNV also induces the expression of hepc1 mRNA in the anterior kidney and skin of Sockeye salmon [ 64 ]. In the anterior kidney, hepc1 gene expression is directly correlated with the viral load [ 64 ].…”

“…IHNV also induces the expression of hepc1 mRNA in the anterior kidney and skin of Sockeye salmon [ 64 ]. In the anterior kidney, hepc1 gene expression is directly correlated with the viral load [ 64 ]. This suggests that hepc1 may be involved in the control of IHNV replication.…”

“…Salmonids serve as a host for a multitude of parasites that may result in tissue damage and severe inflammatory responses [ 64 , 70 , 71 , 72 , 73 ]. It is not uncommon for co-infection to occur with other parasites or pathogens, thus leading to enhanced immune activation [ 63 , 72 ].…”

Factors associated with severity of naturally occurring piscirickettsiosis in netpen‐ and tank‐reared juvenile Atlantic salmon at a research aquarium in western Canada

“…The earlier onset and increased SRS‐associated mortality in the NP‐reared salmon held under more variable conditions were similar to that in aquaculture in which outbreaks of the disease have been associated with elevated water temperatures (Rees et al, ), algal blooms and severe meteorological events (Cusack, Groman, & Jones, ; Olsen, Melby, Speilberg, Evensen, & Hastein, ). Infection with multiple pathogens may increase the severity of disease in fish (Long, Garver, & Jones, ); however, there was no evidence of co‐infection or pathology of sufficient intensity or severity to explain the increased mortality in the NP‐reared salmon. Rather, our findings support a P. salmonis aetiology for the elevated mortality in tank‐ and NP‐reared salmon that in the latter, was exacerbated by variable environmental conditions.…”

Study on the differentially expressed genes and signaling pathways in dermatomyositis using integrated bioinformatics method

“…Radical S-adenosyl methionine domain-containing protein 2 (RSAD2) is an endoplasmic reticulum associated virus suppressor gene mediated by interferon I. [ 79 ] RSAD2 promotes Th0 cells to differentiate into Th2 cells, and then induces and regulates B lymphocyte activation and autoantibody secretion. [ 80 ] RSAD2 has been found to be related to a variety of autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, and so on.…”